Typical rainwater storage tanks have some method of directing rainwater from the roof of a structure into an opening in the storage tank. Some method is also included that allows stored rainwater to be extracted from the storage tank. Prior art storage tanks are designed to be singular (typically cylindrical) storage tanks with little consideration for geometry or modularity.
A modular rainwater storage tank is designed as a three-dimensional quarter-round shape in embodiments of the present invention. One or more of the modular units may be positioned next to a house or other structure from which rainwater runoff is to be captured. The storage tank is designed with a fill opening and an over flow that allows water from the primary storage tank, connected to a downspout, to be directed to an optional second, third, fourth, etc. storage tank. The quarter-round design allows three storage tanks to be efficiently positioned around a right angled corner while increasing the rigidity of the storage tank system. The quarter-round shape increases the rigidity over a typical square storage tank. While a square storage tank has increased volume, the radius R of the quarter-round storage tank need only be increased to 1.128R to have a volume equal to a square storage tank with side equal to R. The top of the storage tank may have a raised rim wide enough to place a fill hole the size of a downspout. The raised rim has one or more channels configured so adjacent storage tanks may be coupled with a channel piece that aids in directing overflow water between storage tanks. An overflow adapter or a water block may be positioned in an overflow channel depending on whether multiple storage tanks are cascade-connected via a channel piece positioned in adjacent channels. A U-shaped clip may be inserted over the raised rims of adjacent storage tanks to increase the rigidity of a multiple storage tank system. A side wall of a storage tank may have a threaded hole configured to accept a faucet for draining each storage tank.
In alternative embodiments, the top lid of the tank is sloped so that the rainwater flows towards a fill hole.